By Dan Williams
TEL AVIV (Reuters) - Israeli armed drones use gravity bombs that produce no noise or smoke as they fall, making them hard for enemies to anticipate or evade, and the largest model of the aircraft can carry up to a tonne of munitions, its military says.
After more than two decades of secrecy, Israel in July went public about its pioneering armed drones developed as part of an array of stand-off surveillance and striking options since it was blindsided by tank incursions during a 1973 war.
In November, an Israeli general detailed the two corps - air force and artillery - that operate the drones, both against Palestinian foes close to home and possibly targets as far away as Iran or Sudan.
Such drones are remote-piloted, relaying video or dropping bombs before returning to base. They are distinct from the kamikaze drones that Iran said were used in a weekend attack on a defence plant in Isfahan, an incident on which Israel has declined to comment.
Briefing Reuters, a senior Israeli military officer said the armed drone fleet includes the passenger plane-sized Heron TP, made by state-owned Israel Aerospace Industries Ltd, and Elbit Systems Ltd's smaller Hermes.
The former, the officer said, "is the heaviest drone that the IDF (Israel Defence Forces) has, which can carry munitions, with an effective payload of around a tonne".
But, in an apparent allusion to the need to balance out payloads carried under the drones' wings, the officer added: "This does not necessarily mean they can carry a one-tonne bomb. It very much depends on the positioning of the munitions."
Israeli manufacturers do not publicise the armed capabilities of the drones, under what industry sources have described as a Defence Ministry secrecy policy.
MAJOR DRONE OPERATOR
With its capabilities closely tracked by the global defence industry, Israel has become one of the largest drone operators in the Middle East and a net exporter, according to the Royal United Services Institute, a London think tank.
The Israeli officer, not identified in line with military requirements given the sensitivity of the subject, said any sales of bomb-capable drones would be government-to-government, negating the need for publicity.
All the drone munitions are Israeli-made, the officer said, and "come down in free-fall, and can reach the speed of sound".
Such bombs, unlike the Hellfire missiles sometimes fired by U.S. drones, would not have propulsion systems that generate the tell-tale noise and smoke of fuel afterburners.
The officer declined to give further details on the munitions, saying only that, by design, when an armed drone attacks "no one will hear it, no one will see it coming".
An example of a drone target could be fast-moving guerrillas, spotted and attacked before they can launch a rocket, other Israeli officials have said.
Yet this would assume enough altitude so that the drones' propeller engines cannot be clearly heard on the ground.
In winter wars, like Israel's in Gaza in 2008-2009, the drones have to be flown below the clouds for their targeting cameras to work, meaning they might be audible.
"You lose the element of surprise," the officer said.
Despite deploying sophisticated armed drones, the majority of Israel's UAV (Unmanned Aerial Vehicle) inventory is unarmed given the main function of intelligence for ground forces, the RUSI think tank said in an online report.
(Writing by Dan Williams; Editing by Robert Birsel and Andrew Cawthorne)